Global navigation satellite systems (GNSS) have been used primarily for position determination for navigation purposes. In essence, such systems are based on the propagation time measurement to different satellites. At least four satellites must be visible at any point in time to be able to reliably and unambiguously determine a position. The receiver is able to determine its own position from the position of the satellite and the signal propagation times.
In general, distance-transmitting sensors, which are upwardly oriented and are thereby able to directly establish whether an obstacle is present within the range above the vehicle that can be interpreted as a ceiling, are used for detecting ceilings, or roofing. Such information can be used, for example, to assess an ambient temperature value obtained using a temperature sensor, and to not use potentially encountered milder ambient temperatures, occurring temporarily when traveling through a tunnel, as a basis for a range prediction by the on-board computer.
The identification of a route that is covered overhead can be used for a wide variety of comfort functions. In this context, a control system for a vehicle having a navigation system for detecting a current position of the vehicle and further having a control unit coupled to the navigation system is known from DE 10 2008 056 907 A1. In DE 10 2008 056 907 A1, at least one vehicle component can be activated, using the control unit, as a function of the current position of the vehicle, and at least one global position of the vehicle can be predefined by a user. According to one disclosed embodiment of DE 10 2008 056 907 A1, the navigation system may identify when a route that is covered overhead, such as a tunnel, is about to be traversed, and an information signal indicating this traversing can be transmitted from the navigation system to the control unit. The control unit can then use this information signal to activate the at least one vehicle component.
At present, a large number of vehicles are not equipped with sensors that are upwardly oriented. As a result, the ceiling or roofing cannot be reliably detected.
Additional sensors, which are provided for the purpose of detecting the ceiling, incur additional costs and usually offer advantages in a limited number of situations. If the sensors are dispensed with, a ceiling cannot be identified, and a garage parking space thus cannot be validated even after the parking process. Such a function is required, for example, for automatically parking the vehicle in a garage. A vehicle user can leave the vehicle and start the garage parking function of the vehicle. The vehicle can then park itself within a limited perimeter, the extent of which can be predefinable, search for the garage, and park in the garage. Due to a lack of sensors in many presently available vehicles, a failure of the parking process cannot necessarily be detected. This is because such sensors could be used to validate the success of the automatic parking process in the garage by providing a piece of “ceiling above vehicle” information. It could be possible, for example, that the vehicle simply comes to a halt between two houses because the contour of the houses is misidentified as a garage by conventional vehicle sensor systems. Moreover, conventional distance-transmitting sensors can frequently supply faulty detections when the vehicle is being parked under a tree, for example. If only a few sensors are present, it is possible for many detected objects to be erroneously identified as ceilings.
Furthermore, a method for operating a device, in particular a navigation device for a motor vehicle, is known from DE 10 2007 020 434 A1. The device includes a processor, a signal receiver for receiving position signals, in particular GPS signals, a road network database, which also includes position data on tunnels (tunnel attributes), a position ascertaining unit, which determines the current position of the vehicle, a display unit, and a display controller for controlling the settings of the display unit, in particular for regulating the brightness and/or a color scheme of the display unit. The display controller is able to vary the setting of the display unit when driving through a tunnel (tunnel mode). The method includes the steps of ascertaining the vehicle position, taking the received position signals into consideration, and automatically activating the tunnel model of the display unit using the display controller, immediately or with a certain time delay, when the ascertained vehicle position includes a tunnel attribute, and the received position signals drop below a predefined signal quality. In this way, a GNSS receiver, which is already present in many vehicles, can be used to detect ceilings or covered areas and/or when these are entered and/or exited.
However, this method has the disadvantage of being dependent on an available road network database and being applicable only to accordingly expansive structures, such as tunnels, in which the loss of the GPS signal, and the drop below the predefined signal quality associated therewith—as claimed in DE 10 2007 020 434 A1—are very suitable for reliably identifying the entering of a tunnel.
For the determination of a position of a vehicle when GNSS signals are shielded, for example in a parking garage, a method is known in this context from DE 10 2012 223 970 A1 for determining initial data for the determination of position data of a vehicle based on vehicle dynamics data. The method includes the steps of associating a defined ambient condition with a defined position of the vehicle, detecting an ambient condition, and using the defined position as initial data if a comparison of the detected ambient condition and the defined ambient condition satisfies a predetermined condition.
The features and advantages of the present embodiments will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.